Non-inductive resistance.



No. 874,023. PATENTED DEG. 1'7, 1907.

J. F. MOELROY- NON-INDUGTIVE RESISTANCE.

APPLICATION FILED T11R21. 1907.

1:111 [112 5 =5 E 5 lnvEniclr mum 5 M 135 a tween until one layer is complete, the wire UNITED STATES PATENT OFFICE.

JAMES F. McELROY, OF ALBANY, NEW YORK, ASSIGNOR TO CONSOLIDATED UAlt-lll lATlNG COMPANY, OF ALBANY, NEW YORK,

A CORPORATION OF WEST VIRGINIA.

NON-INDUCTIVE RESISTANCE.

Specification of Letters 1': ate-at.

Patented Dec. 17, 1907.

Application filed Tebruary 21. 1907. Serial No. 358.649.

To all whom it may concern:

Be it known that I, JAMEs F .l M cEnnoY, a citizen of the United States, residing at Al ban in the county of Albany and State of New York, have invented certain new and useful Improvements in N on-Inductivc l.i.e sistances, of which the following is a specification.

This invention relates to electrical resist ances, and it has for its object to provide a resistance element in a compact form con taining a great length of wire and substantially free-from magnetic and sell-inductive eiiects.

Briefly stated, I attain this object by winding on a suitable core or support, a series of coils or helices of wire having a high specific resistance and winding the successive coils so that their polarity is opposite and counterbalanced, thereby avoiding the magnetic effects of the coils and also permitting the resistance element to be cored and incased with iron without either producin or adding to such magnetic effect. I furthermore prefer to wind each layer with air spaces between the turns and to secure these turns by painting each layer with an insulating varnish, and I also prefer to place insulating sheets, such as paper sheets, between adjacent wire layers.

Of the accompanying drawings, Figure 1 represents a sectional view of my improved resistance element or structure, showing successive layers broken away. Fig. 2 represents a cross section taken near one end of the winding. Fig. 3 represents an end view.

The frame of the resistance device as shown is composed of a central core or sup port such as an iron tube havin head pieces or plates 11, 12 at its ends to winch it is secured by a rivet 13 in the case of the head 11, and by a screw-thread 14 in the case of the head 12. These heads are suitably flanged to receive between them and sup wort the ends of an outer tubular casing 15 which may be a section of iron pipe surrounding the resistance wire.

The electrical resistance is composed of a series of layers or helices 16 of wire forming one continuous electrical conductor of high specific resistance, and the method of winding these layers is to place the core in a lathe having an automatic screw feed and wind the successive turns of wire with air spaces bebeing bare or uncovered. I may use covcred wire pitched only bythc thickness of the wire and its covering but prefer the construction described as a'll'ording better insulation at less cost. When one layer is complete it is painied over with a suitable insulating varnishso as to securely fix the wire in place and insulate it, and then a layer of insulating paper i7 is wrapped about the Wire layer so as to cll'cctively insulate it from the r succeeding layer. A layer of insulating paper is also previously wound about the iron core 10 to insulate the first layer from this core. Another layer of wire is then wound aroundthe first layer against the insulating paper but is wound in the opposite direction l so that its magnetic poles are opposed to and neutralize the magnetic poles of tho preceding layer or helix. This may be done by reversing the structure end for end in the lathe and producing the feed from the same point and in the same direction as for the preceding layer, or the structure may be left in the lathe spindles in its original position and the direction of rotation of the lathe spindles re versed while the feed is also reversed, so that the new coil starts back from where the old coil ended as regards position in the lathe.

The reversal of the winding in successive layers is indicated in Fig. 2 Where it is seen that the ends of adjacent layers form a return loop. The heavy circular lines between the wires in this view indicate the insulating paper sheets and it will be seen that the loop formed by the beginning of each succeeding coil and the end of the preceding coil is turned about the longitudinal edge of the insulating sheet and is anchored thereby so as to prevent any tendency of the helix to uncoil. Thus the sheets serve as anchors for the ends of the helices in addition to their function of insulating layers, and thereby avoid the necessity for any separate anchoring means. The third layer is wound so as to have the same direction and the same polarity as the first layer, and the l l l l r v l l l l 1 fourth the same as the second, and so on until the structure has been built up to a depth giving the desired resistance, each wire layer being varnished and insulating paper layers bemg inter osed between the wire layers as previous y' described. The two ends of the wire are led out through the same or opposite ends of the structure as desired.

A non-inductive resistance of the described character may be employed in operating electric signal bells on high-voltage power circuits, as described in my co-pending application, Serial No. 358,648 or in other situations.

1 am aware that non-inductive resistances have been made by winding two parallel wires side by side on a core and connecting them as one conductor so that the current flows in opposite directions in the two parallel helices which are like a double screw thread, whereby the magnetic poles are neutralized. While this construction answers for comparatively small currents it is neither reliable nor safe for high-power circuits such as those of electric-traction roads for which my present invention is specially contrived, since the double or two-wire winding would provide too great a difference of potential between points in the coil located very close together. Thus near the two terminals of the coil the entire difference of potential established by the resistance occurs between adjacent turns. Short-circuiting is thus practically inevitable if any high-voltage current is used and the tendency multiplies when it becomes necessary to wind the wire in successive overlying coils in order to obtain sufiicient resistance in a com act form. In my resistance device it wil be noted that the difierence of otential between any two adjacent turns 0 the wire is very sli ht and the points of greatest potential di erence, namely the two terminals, are

separated by the entire insulation. improvement in a non-inductive resistance constitutes the main feature of my invention.

I am also aware that it is not new to wind resistance coils with open spacing and paint them with an insulating varnish and I do not claim such a practice broadly.

1 claim:

1. A non-inductive resistance comprising a support, and a conductor laid thereon in superposed layers having opposite polarities.

2. A non-inductive resistance comprising a wire conductor composed of concentric layers wound in opposite directions so as to neutralize their magnetic polarity.

3. A non-inductive resistance comprising -a central sup orting core, an electrical conductor woun thereon in concentric layers having an opposite direction and counterbalanced polarities, together With sheets of insulating material wrapped about the successive layers to provide insulation between This said layers, the beginning of each succeeding coil forming, with the end of the preceding coil, a loop turned about the longitudinal edge of the interposed sheet of insulating material and anchored b said sheet.

In testimony whereof have hereunto set my hand in the presence of two subscribing witnesses, the 16th day of February, 1907.

JAMES F. MCELROY.

Witnesses:

BEULAH CABLE, Ermns'r D. JANSEN. 

